package com.mall.common.xss;

import com.mall.common.utils.StringUtils;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 防止XSS攻击的过滤器
 * Created by zhonglin on 2020/4/8.
 */
public class XssFilter
    implements Filter {

  /**
   * 排除链接
   */
  public List<String> excludes = new ArrayList<>();

  /**
   * xss过滤开关
   */
  public boolean enabled = false;

  @Override
  public void init(FilterConfig filterConfig)
      throws ServletException {

    String tempExcludes = filterConfig.getInitParameter("excludes");
    String tempEnabled  = filterConfig.getInitParameter("enabled");
    if (StringUtils.isNotEmpty(tempExcludes)) {
      String[] url = tempExcludes.split(",");
      for (int i = 0;
           url != null && i < url.length;
           i++) {
        excludes.add(url[i]);
      }
    }
    if (StringUtils.isNotEmpty(tempEnabled)) {
      enabled = Boolean.valueOf(tempEnabled);
    }
  }

  @Override
  public void doFilter(ServletRequest request,
                       ServletResponse response,
                       FilterChain chain)
      throws IOException, ServletException {

    HttpServletRequest  req  = (HttpServletRequest) request;
    HttpServletResponse resp = (HttpServletResponse) response;
    if (handleExcludeURL(req, resp)) {
      chain.doFilter(request, response);
      return;
    }
    XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);
    chain.doFilter(xssRequest, response);
  }

  private boolean handleExcludeURL(HttpServletRequest request,
                                   HttpServletResponse response) {

    if (!enabled) {
      return true;
    }
    if (excludes == null || excludes.isEmpty()) {
      return false;
    }
    String url = request.getServletPath();
    for (String pattern : excludes) {
      Pattern p = Pattern.compile("^" + pattern);
      Matcher m = p.matcher(url);
      if (m.find()) {
        return true;
      }
    }
    return false;
  }

  @Override
  public void destroy() {

  }

}